Adjustable face mill cutter



y 6, 1965 n L. WHITMORE I ,604

ADJUSTABLE FACE MILL CUTTER 3 Sheets-Sheet 1 Original Filed Aug. 23. 1960 FIG.

FIG.

ATTORNEY D. L. WHITMORE ADJUSTABLE FACE MILL CUTTER July 6, 1965 3 Sheets-Sheet 2 PRIOR ART Original Filed Aug. 23, 1960 FIG. IO

FIG. 9

July 6, 1965 D. L. WHITMORE 3,192,604

ADJUSTABLE FACE MILL CUTTER Original Filed Aug. 23, 1960 3 Sheets-Sheet 3 56% FIG. ll PRIOR ART 1' II I I8 32 1 3| Io 57 flx X A i a fi 54 23. Q

FIG. l2

X 1 1 762 w W as 5? v e2 e3 FIG. I3 FIG. I4

United States Patent 3,192,694 ADJUSTABLE FACE Mill, CUTTER Donald L. Whitmore, Webster, N.Y., assignor to The Gleason Works, Rochester, N321, a corporation of New York Continuation of application Ser. No. 52,998, Aug. 23,

195% This application Aug. 9, 11963, er. No. 391,623

11 Claims. (Cl, 29-105) This is a continuation of application Serial No. 52,008, filed August 23, 1960, and a continuation-in-part of application Serial No. 802,160, filed March 26, 1959.

The invention relates to an improved face mill cutter of the inserted blade type for finish cutting spiral bevel and hypoid gears and similar toothed parts.

Cutters of this kind comprise a disc-shaped cutter head having slots in its periphery for seating the shanks of the blades. Inserts comprising wedges or shims, or both, for adjusting the blades radially, are usually interposed between the shanks and the bottoms of the slots, and the blades are secured by headed screws which extend through openings through the shanks and the inserts and are screwthreaded into the head.

An object of my invention is a cutter of this kind having a greater number of blades than has been practicable heretofore, and which can be trued more easily and quickly.

Another basic object of the invention is to improve the stability of the blades in the head, to better retain their initial or adjusted positions in the presence of cutting impacts, and thereby lengthen cutter life and improve the surface finish produced on the work.

In the accompanying drawings:

FIGS. 1 and 2 are front face views respectively of an outside cutter, for cutting the concave sides of gear teeth, and of an inside cutter, for cutting the convex sides of the teeth;

FIGS. 3 and 4 are radial sectional views, respectively in plane 3-3 of FIG. 1 and plane 4-4 of FIG. 2;

FIG. 5 is an enlarged fragmentary sectional view through a blade holding screw and the adjacent part of the cutter head;

FIG. 6 is a similar fragmentary view through a conventional cutter;

FIGS. 7 to 10 are respectively front, outside, inside and bottom views of an outside cutting blade shown in FIGS. 1 and 3;

FIG. 11 is a side view of a conventional cutter blade mounted in a cutter head;

FIG. 12 is a view similar to FIG. ll, but showing a ct ter blade of the present invention mounted in its cutter head;

FIGS. 13 and 14 are diagrammatic views of cutter blades and related portions of cutter heads, indicating forces applied thereto.

The particular cutters shown in the drawings are of right hand, i.e. are adapted to cut while rotating clockwise as viewed from the back. The cutter of FlGS. 1 and 3 contains outside cutting blades, one of which is shown in FIGS. 7 to 10, while that of FIGS. 2 and 4 contains inside cuttingblades. Although the cutting portions of the outside and inside cutting blades are of different shape, the blade shanks and their connections to the cutter head are substantially identical. The particular cutters shown are designed for the finish cutting of pinions, whose opposite tooth sides are usually finish cut in separate operations and with different cutters, whereas both tooth sides of the mating gears are usually finish cut in a single operation, the gear cutter therefore containing both outside and inside cutting blades, usually arranged alternately in the cutter head.

Edhlfifid Patented July 6, 1965 Both of the cutters shown in FIGS. 1 to 4 comprise a head 1% of through-hardened tool steel with a tapered bore 11 for seating on the spindle nose of a gear cutting machine. A plate 12 secured to the head by screws 13 has a seat 14 for the head of a screw (not shown) which secures the cutter to the spindle. The axis of rotation of the cutter and spindle is designated 15. The head has about its periphery a plurality of blade-receiving slots 16 separated by lands 37. These slots are orthogonal, with their opposite sidewalls disposed in parallel planes which are parallel to and equally ofiset from the axis 15, and are perpendicular to the plane front face 18 of the head.

Wedges 19 are seated on the bottom walls of the slots, which, as shown in FIGS. 3 and 4, are slightly inclined to the, cutter axis so that the outer faces 21 of the wedges will be parallel to the cutter axis and perpendicular to the plane face 18. The wedge faces 21 and also the bottom walls of the slots are perpendicular to the side walls of the slots. Where necessary to the desired radial positioning of the blades in the head, shims 22 having parallel upper and lower faces are interposed between the wedges and the shanks of the cutter blades.

As best shown in FIGS. 7 to 10, each outside blade comprises a cutting portion positioned to project forwardly from the head ll) and an attaching or shank portion for connection to the head. The cutting portion has an outside side cutting edge 24 at the acute-angled juncture of its front or sharpening face 25 and its cutting side face 26, a non-cutting side edge 27 at obtuse-angled juncture of its clearance side face 28 and front face 25, and tip face 29. The shank of the blade is of generally T-shape as viewed in FIG. 8, comprising a stem to fit the related slot 16 and arms which constitute abutments 31 and 32 for seating on the plane front face 18. The inner faces 33 of the blade shanks seat on the outer faces of the shims 22, or, if the latter are omitted, on the outer faces of the wedges 19. The faces 34 and 35 of the shanks are plane and parallel, and closely fit the parallel sides of the slots; and the outer faces 36 are plane but are inclined to inner faces 33 by an acute angle, of ten degrees in the illustrated embodiment, for seating the heads 37 of blade-holding screws 38. The shanks of these screws extend through correspondingly inclined openings 59 through the blade'shanks and through approximately aligned openings through the related wedges and shims, and are screw-threaded into the head fill at the bottoms of the slots 16. Axes ll of the screws are perpendicular to shank faces 36 and lie in planes radial of the cutter axis 15, being inclined to that axis at an acute angle, of eighty degrees in the illustration. The screw axes are parallel to and midway between the side walls of the related slots 16.

The relative inclination of the outer and inner faces 33 and as of the blade shanks has been made slightly larger than the minimum angle which will assure the blades being drawn into the cutter head in the cutter axial direction as well as in a direction radial of the cutter axis when screws 53 are tightened. According to the invention surfaces 42 and &3 of both abutments 31, 32 seat firmly on plane face is of the cutter head as a result of this inward draft. As will be apparent to those skilled in the art, the fact that the parallel faces 34' 35 and inner face 33 of the blade shanks closely fit the side walls and effective bottom walls (shims 22) of slots 16, makes it necessary for such seating of surface 42, 43, that these surfaces be accurately co-planar and accurately perpendicular to faces 33, 34, 35. in practice with cutters of the sizes currently .used for automobile axle drive gears, I find it desirable for best results to maintain the surfaces 42, 43 coplanar within five ten-.thousandths of an inch and perpendicular to face .33 within two ten-thousandths of an inch, To

facilitate the accurate finishing of the surfaces 53, 3d, 42, 43, grinding relief ,rooves 4-4 are provided at the jtmctures of surfaces 33 and 42 and of surfaces 36 and 43 prior to t eir final grinding. The thickness of the abutments 31 and 32 in an axial direction, i.e. the distance between the front face 1-3 of the cutter head and the innermost edge 25A of the sharpening face 25, is such that repeated resharpening, whichmay gradually move the sharpening face 25 back to a position such as that shown in broken lines in FIG. 9, does not affect the abutment 31 with respect to its seating on the cutter head.

As shown in FIGS. 7 to 10 the seating surfaces 42, 43 of the abutments are rectangular, and of a lengthcorrespending substantially to the maximum thickness of the shanks between inner and outer faces 33, 35, dimension T in FIG. 7. This substantial lengthwise extent of surfaces 42., 43 enables the blades to have a firm and stable seat on the face 13 of the head in any of the various positions to which they may be adjusted by wedges i and by the omission or inclusion of shims The wedges are adjusted forward or backward in the slots 16 in a known manner by turning wedge-adjusting screws 45 when the blade-holding screws 37, are loosened. Screw-s 45 engage in recesses 45 in the wedges are screw-threaded into the cutter head. Their axes, 4'7, lie in the same radial planes as the axes d1 of the related blade-holding screws.

As shown in FIG. the blade holding screws 3.3 and the mating screw holes in the head ltd have buttress threads, the particular ones that are illustrated having a pressure flank angle of seven degrees and a trailing flank angle of forty-five degrees. That is, the pressure flank 48 is at an angle A of seven degrees with respect to a perpendicular of screw axis 41, and the trailing flank 49 is at angle B of forty-five degrees to such perpendicular.

For the purpose of comparison, a conventional prior art cutter head-cutter blade assembly has been illustrated in FIGS. 6 and 11. In these views the reference numerals have been primed to distinguish them from the numerals for corresponding parts in FIGS. 1 to 5, 7 to 10,

12 and 13. The cutter head is like that of the present invention except that the axis 42*. of the holding screw 38' is perpendicular to the cutter axis instead of inclined at an acute angle thereto, and the screw-thread formation is conventional, both the pressure flank angle A and trailing flank angle B being thirty degrees. The conventional blade does not have a leading end abutment corresponding to 31, but only a trailing end abutment 32.

Difficuity is encountered in accurately truing the prior art cutters, particularly when an attempt is made to in crease the number of blades by reducing the widths of the inter-slot lands 17. In truing, each blade around the cutter is adjusted by loosening the holding screw, adjusting the wedge and then retightening the holding screw. The loosening and retightening disturb the position of a previously adjusted adjacent blade, and the smaller the width of lands 17 and the spacing of the screws 38', the greater this disturbance becomes.

The rigidity of the cutter heads may be increased by making them of through-hardened steel. This has been found to decrease the disturbance due to loosening and retightening of the holding screws and to make possible a reduced width of lands 17' and a corresponding increase in the number of blades that can be accommodated in a head of given diameter. However the use of throughhardened steel for the heads has aggravated another difliculty: In order to seat a blade firmly against the front face of cutter head, the blade is lightly tapped with a suitable implement just prior to retightening the holding screw. With hardened heads there is a greatly-increased tendency for the blade, which is also hardened tool steel, to bounce away from the head when it is tapped. I have found that such tapping can be eliminated by inclining the holding screws so that as they are tightened they draw abutments on the blades against the front face of the head. This however increased the disturbance of adjacent blades. Strangely, this effect was greater in right hand than in left hand cutters.

I have found that by using screws of the buttress type, FIG. 5, in place of conventional screws, FIG. 6, the disturbance to adjacent blades is substantially reduced, making cutter truing less difiicult although still not to the degree desired. The reason for the improvement is believed to be :the following: When the angle A is nearly equal to or less than the static angle of friction for lubricared steel surfaces, an axial load on the screws, represented by vector 51, cannot overcome frictional resistance of surface .8 to lateral shifting, so that the vector force 52, which in any case is very small, is unable to displace the metal of head 10 around the screw in a transverse direction, i.e. in the direction of vector 52. Referring to PEG. 1 it will be seen that if transverse strains 52 resulting from loosening or tightening the blade-holding screws are so small that they do not extend to the intermediate zone of the head between planes 53, which touches the zone beneath adjacent blades and embraces the land T7 between them, then such strains cannot eifcct the adjustment of an adjacent blade. That is, loosening or tigh ening of screw a, FIG. 1, will then not affect the position of the blade held by screw b. Obviously a similar reduction in the disturbance of adjacent blades will result from the use of screws having a pressure flank angle of less than seven degrees, i.e. between 0 and 7. However such screws are dlfilClllt to manufacture with the required accuracy.

With conventional screws, FIG. 6, wherein the pressure flank and trailing flank angles A and B are both greatly in excess of the static angle of friction, the transverse forces 52', resulting from axial loads on the screws 38' exceed the frictional resistance of thread surface 48 to lateral sliding motion, so that lateral displacement occurs in the portion of head 10' immediately around the screw holes when then the screws are loosened or tightened. This results in the strains 52'', PEG. 1, extending well into the zone between planes 53, so that the adjustment of a blade held by an adjacent screw is disturbed.

Also I have found that in truing there is less disturbance to adjacent blades when an abutment, such as 31 or 32 is provided at that end of the blade which is moved against the cutter head by torque in the direction in which the blade-holding screw is tightened. Conventionally the screws of both right and left hand cutters have right hand threads, and accordingly my finding is that a leading end abutment 31 should be provided on a right hand cutter and a trailing end abutment 32 on a left hand cutter. The reason, which explains the previously observed difference between cutters of right and left hand, is believed to be as follows: Referring to FIG. 11, a conventional cutter blade has an abutment 32 on its trailing end for seating on the front face '18 of the head. When the holding screw 38 is tightened, by turning it clockwise, the torque resulting from frictional cont-act of the screw head 37' tends to rotate the blade clockwise, producing forces against the inter-slot lands 17' such as are indicated by arrows 54. I have found, by measurement, that these forces decrease width dimensions 55' of adjacent blade slots, and increase width dimensions 56' at the opposite ends of these slots. When the cutter of FIG. 11 was modified to incline the screw axis 41 (in the way axis 49 is inclined in FIG. 3) to draw abutment 32' against surface 18, I discovered that the changes of dimensions 55 and 56 incident to tightening the screw greatly increased. From this I concluded that the increased force on the blade, in the direction of arrow 57, together with the opposite resisting force exerted by the abutment at 32', constituted a force-couple tending further to rotate the blade clockwise in the head, thus augmenting the forces 54 and thereby increasing the disturbance to adjacent blades. These considerations led to the manufacture of blades for right hand'cutters having abutmeuts 31 at their leading ends, substantially. as

shown in FIG. 13, instead of having abutments at their traihng ends.

Referring to FIG. 12, and disregarding abutment 52, when the screw of such a blade is tightened, the blade is drawn inwardly, in direction 57. This together with the resisting force imposed on abutment 31, represented by arrow 58, constitutes a force-couple tending to rotate the blade counterclockwise in the head. It is opposite to and therefore tends to cancel out the effect of the opposing force-couple, represented by arrows 54, 54, resulting from torque imposed frictionally by rotation of screw 38. The lands 17, 17 are therefore relieved from the source of distortion explained in connection with FIG. 11.

Cutters with these blades were excellent insofar as concerns ease of accurate truing. A blade repeatedly loosened and then retightened to the same torque load applied to the holding screw would accurately return to its original position, and the truingof one blade would not appreciably disturb a neighboring blade. However these blades were not wholly satisfactory from the standpoint of stability under cutting loads. That is, an accurately trued cutter after cutting one or a few gears would be checked, and it would be found that the ctting edges of its blades no longer tracked accurately. Referring to FIG. 13, I believe that the inward component force 57, exerted by tightening of the holding screw, strains the shank of the blade, and that when this is augmented by a cutting impact, as when the blade enters a heavy cut or strikes a hard spot in the workpiece, a torque is applied to the blade which is additive to the force 57, and displaces the blade slightly in the cutter head. Such an additive torque may be exerted by a tangential cutting load in the direction of arrow 59 in the case of a right hand cutter, cutting from left to right in PEG. 13, or by an axial cutting load in the direction of arrow 61 in the case of a left hand cutter, cutting from right to left in this view.

It will also be observed from FIG. 13 that apart from frictional restraint, the blade is held against clockwise displacement about the axis of the blade-holding screw only by the abutment of the cutter head indicated by arrows s2, and is held against counterclockwise displacement by the abutment of the head indicated by arrows 63. In both cases stability therefore depends upon constraint imposed by the side walls of the slot in the cutter head.

With the improved cutter blades shown in FIGS. 7 to 10, with abutments at both their leading and trailing ends, the stability of the blades in the head is greatly improved. A notable result of this improvement is that many more gears than formerly can be out before resharpening 'of a cutter becomes necessary, presumably because of the more accurate tracking of the successive blades which results in more equal distribution of cutting loads. The probable reason for this improvement may be seen from FIG. 14. The rearward component 57 of the force exerted by the holding screw firmly draws both abutments 31 and 32 against the plane face 18, this rearward draft being directly opposed by the head as indicated by arrows 64 and 65. Cutting impact loads, regard-less of whether they tend to displace the blade clockwise or counterclockwise about the axis of the holding screw, are directly resisted by either force-couple 57,

4 or by force-couple 57, 65, without dependence upon the side walls of the slots. Also axial cutting loads, whether at 6 5, in the case of a right hand cutter, or at 67, in the case of a left hand cutter, are directly resisted by abutment of the cutter head at 64 or 65.

Having now described the preferred form of cutter and cutter blades, what I claim as my invention is:

1. A face mill cutter comprising a head having a multiplicity of slots in the periphery thereof, inserted blades having cutting portions extending forwardly from the front of the head and having shanks extending into said slots and confined by the walls of said slots, and headed '6 holding screws extending through said shanks and screwthreaded into threaded bores in the head at the bottoms of said slots, the threads of "said screws and openings having a pressure flank angle not substantially exceeding the static angle of friction thereof for minimizing displacement of the slot walls confining an adjacent blade when a holding screw of one blade is tightened or loosened.

2. A cutter according to claim '1 in which said threads of the holding screws and bores in the head are buttress threads.

3. A cutter according to claim 1 in which said head has a plane front face, the shank of each blade has, as surfaces for seating in the related slot, opposite parallel faces perpendicular to said front face and an inner plane face perpendicular to said front face and to said parallel faces, the shank has, for seating on said front face, abutments at both its leading and its trailing ends overhanging said parallel faces, the seating surfaces of said abutments being co-planar and perpendicular to said parallel faces, and the shank also has, for seating the head of the related holding screw, a plane ,outer face which is perpendicular to the axis of the screw and to said parallel faces, and is inclined to said inner plane face in the sense, and at an angle exceeding the static angle of friction of the blade against steel, to cause said abutments to be drawn against said front face upon tightening of the screw.

4. A cutter according to claim 3 in which said surfaces of said abutments are of a length corresponding substantially to the maximum thickness of the shank between said inner and outer faces.

5. A face mill cutter comprising a head having a multiplicity of slots in the periphery thereof, inserted blades having cutting portions extending forwardly from the front of the head and having shanks extending into said slots, and headed holding screws extending through said shanks and screw-threaded into threaded openings at the bottoms of the slots, the head having a plane front face, the shank of each blade having, as seating surfaces within the related slots, opposite parallel faces perpendicular to said front face and an inner plane face perpendicular to said front face and also perpendicular to said parallel faces, the shank having, for seating on said front face, abutments at both its leading and its trailing ends overhanging said parallel faces, the seating surfaces of said abutments being co-planar and perpendicular to said parallel faces and to said inner plane face, and the shank also having, for seating the head of the related holding screw, a plane outer face which is perpendicular to the axis of the screw and to said parallel faces, and is inclined to said inner plane face in the sense, and at an angle exceeding the static angle of friction of the blade against steel, to cause said abutments to be drawn against said front face upon tightening of the screw.

6. A cutter according to claim 5 in which said surfaces of said abutments are of a length corresponding substantially to the maximum thickness of the shank between said inner and outer faces.

7. A blade for insertion in a face mill cutter head which has a blade receiving slot on its periphery and a screw-threaded bore for a blade holding screw opening through the bottom of the slot, said blade comprising a shank adapted to extend into such slot and a cutting portion projecting forwardly from the shank, the shank having, for seating in such a slot, opposite parallel faces and an inner plane face perpendicular to said parallel faces, the shank having, for seating on the front face of the cutter head, abutments at both its leading and its trailing ends overhanging said parallel faces, the seating surfaces of said abutments being co-planar and perpendicular to said parallel faces and to said inner plane face, the shank also having for seating the head of such holding screw, a plane outer face which is perpendicular to said parallel faces and inclined to said inner face at an 7 acute angle exceeding the static angle of friction of the blade against steel, and the shank further having a bore therethrough between said inner and outer faces for passing the shank of such screw.

8. A blade according to claim 7 in which said seating surfaces of said abutments are of a length corresponding substantially to the maximum thickness of the shank between said inner and outer faces.

9. A blade according to claim 8 in which said surfaces of the abutments are substantially rectangular and are separated from said parallel faces by relief grooves.

10. A blade according to claim 9 in which said shank, including said abutments thereof, is rectangular in a plane perpendicular to said parallel faces and said inner face.

11. A blade for a face mill cutter, of the kind having.

inserted blades Whose shanks seat in slots in a cutter head and have abutrnents seating against a plane front face of the head, the shanks being secured to the head by headed holding screws which extend with clearance through the shanks and are screw-threaded into the head at the bottoms ofthe slots, said blade being characterized in that its shank has,as seating surfaces, opposite parallel side faces and an inner plane face perpendicular to said parallel faces, the shank having abutinents at both its leading and trailing ends overhanging said parallel faces, the seating surfaces of said abutments being coplanar and perpendicular to said parallel side faces and to said inner plane face, the shank having an outer plane References Qited by the Examiner UNITED STATES PATENTS 1,060,749 5/ 13 Freddrick 2996 1,629,667 5/27 Knipple 2996 1,969,843 8/34 Head.

2,024,494 12/35 Wildhaber.

2,125,943 3/ 38 McMullen.

References fired by the Applicant UN TED STATES PATENTS 1,168,356 1/16 Weaver. 1,274,466 8/ 18 Stewart et al. 2,129,056 9/38 Gleason. 2,270,003 1/ 42 Head. 2,348,759 5/44 Sneed. 2,524,301 10/ 5O Bauer. 2,646,611 7/53 Bauer. 2,930,112 3/60 Thomas. 2,947,062 8/60 Spear.

WILLIAM W. DYER, JR., Primary Examiner. 

1. A FACE MILL CUTTER COMPRISING A HEAD HAVING A MULTIPLICITY OF SLOT IN THE PERIPHERY THEREOF, INSERTED BLADES HAVING CUTTING PORTION EXTENDING FORWARDLY FROM THE FRONT OF THE HEAD AND HAVING SHANKS EXTENDING INTO SAID SLOTS AND CONFINED BY THE WALLS OF SAID SLOTS, AND HEADED HOLDING SCREWS EXTENDING THROUGH SAID SHANK AND SCREW THREADED INTO THREADED BORES IN THE HEAD AT THE BOTTOMS OF SAID SLOTS, THE THREADS OF SAID SCREWS AND OPENINGS HAVING A PRESSURE FLANK ANGLE NOT SUBSTANTIALLY EXCEEDING THE STATIC ANGLE OF FRICTION THEREOF FOR MINIMIZING DISPLACEMENT OF THE SLOT WALLS CONFINING AN ADJACENT BLADE WHEN A HOLDING SCREW OF ONE BLADE IS TIGHTENED OR LOOSENED. 